The present invention relates in general to music systems and in particular to an apparatus for generating an additional musical part.
Automatic accompaniment apparatus which generate and play an accompaniment line or subsidiary melody such as countermelody, obbligato, bass line and arpeggio are known. Such apparatus have been incorporated in electronic musical instruments to provide an automatic accompanying function. Typically, a melody (principal part, principal melodic part) is input from a melody keyboard while a chord progression (a succession of chords) is input from an accompaniment keyboard. From the chord progression, the apparatus generates a subsidiary melody. Then a tone generator of the apparatus outputs tones of the subsidiary melody as well as tones of the principal melody.
To generate a subsidiary melody, the prior art apparatus includes stored patterns called accompaniment patterns. Each accompaniment pattern essentially comprises a time (horizontal, durational, rhythm) component i.e., rhythm pattern and pitch line (vertical) component i.e., pitch pattern. In many cases, each accompaniment pattern is provided for a different one of rhythms selected from an input unit of the automatic accompaniment apparatus. Thus, once a particular rhythm has been selected, the apparatus repeats the same rhythm pattern (tone durational series) of the accompaniment without any interaction with a principal melody. Repeating the same rhythm will give a mechanical impression on users.
The other component of the accompaniment pattern i.e., pitch pattern is represented either by a succession of abstract pitches or by a succession of normalized pitches before chord modification.
In a prior art apparatus, a stored pitch pattern is given by a succession of pitches to be played for a particular chord such as C major. In operation, when detecting a chord from the accompaniment keyboard, the apparatus selectively modifies the stored pitch pattern using the type and root of the detected chord to provide the actual pitch line of a subsidiary melody. This arrangement saves the amount of the stored pitch pattern data required for accompaniment. However, the resultant subsidiary (accompanying) melody tends to be monotonous because the actually performed pitch lines are fixedly associated with chords in a one-to-one correspondence.
In another prior art apparatus, each element of a stored pitch pattern (pitch, vertical component of a note) is represented by a chord member identifier. In operation, when detecting a current chord from a chord progression input unit, the apparatus uses the pitch data of members of the current chord to decode each element of the stored pitch pattern (i.e., chord member identifier) for conversion into a concrete pitch. Suppose, for example, a chord with a first member of pitch C, a second member of pitch E, and a third member of pitch A. Then, an element of the stored pitch pattern indicative of a third chord member identifier is converted into a pitch A. This arrangement has the same monotonous problem with the first mentioned prior art because the accompanying subsidiary melody depends only on the chord progression.
Still another prior art apparatus is designed to play a block chord performance with a principal melodic part. This apparatus synchronizes the rhythm of the accompaniment with that of the principal melody by directly using note-ons and offs of the principal melody as those of the accompaniment. The pitches of the accompaniment are formed by chord members having a predetermined pitch relation with a current melody note; for example, the highest chord member is vertically located just below the current melody note. As a result, the melody part and the accompaniment are integrated into a block chord performance in which all pitches are attacked simultaneously. Note, however, that such a block chord performance is a rather unordinary performance and results in a homophonic music. The prior art just stated has no capability of playing a performance having a principal melodic part and an additional melodic part recognized as distinct musical parts from each other.
In polyphonic music pieces composed by human composers, one will find good interactions between musical parts. No successful knowledge representation of interactions among musical parts is known yet. The prior art has disregarded the part-part interactions, or oversimplified them when designing a computer based music system.